Power control



Dec. 10, 1946.

C. F. SCHORN POWER CONTROL Filed March l4, 1942 2 Sheets-Sheet v.1

c. F. scHoRN 2,412,360

A Pow'ER CONTROL Filed March 4, 1942 2 Sheets-Sheet 2 Dec. .10, 1946.

ing I2. l I3 driventhrough a slot I4 at a speed in propor- Patente'd Dec. 10, 1946 POWER CONTROL Carl F. Schorn, Detroit, Mich., assigner to George M. Holley and Earl Holley Application March 4, i942,V serial No. 433,371

4 Claims.

This invention relates to the control of a variable pitch propeller driven by an airplane engine in which the pitch is automatically adjusted to keep the engine at any desired speed.

The object of this invention is to improve the existing power controls so that a manually operated lever will select the speed of the engine desired and that this speed Will automatically select the manifold air pressure desirable at that speed. The product of revolutions per minute and manifold air pressure is roughly proportional to indicated horsepower.

Another object of this invention is to avoid the need for the use of broken links so that straight through pull and push links can be used. As a result, the control unit can be bench-tested, as it is a self -contained unit.

Other objects are to facilitate the operation of the device when cold and to provide means to render the device inoperative when idling the engine, and in both circumstances, to permit the manual operation of the throttle. The reason manual operation is necessary at low speed, especially at idling speeds, is that the centrifugal control of the variable pitch propeller is in operation at low speed.

In the drawings:

Fig. l shows the general elevation of the mechanism.

Fig. 2 shows a plan view of part of the control mechanism.

Fig. 3 shows in cross sectional elevation the combined centrifugal and barometric controls.

Fig. 4 shows a plan View of the manually operated lever and the links connected to it.

Y Fig. 5 shows the normal relation between revolutions per minute and manifold air pressure, and also the relation for best economy.

In Fig. 1 a speed control lever 36 slidabli7 engaging with a quadrant 39 controls the pitch of a propeller 81 through alink 49, rack and pinion 16, centrifugal governor 11, a hydraulic pitch-changing device 18, 19, 80. This device forms no part of this invention and is a well known device in general use for several years. A cam I0 provides a control to change the datum of the centrifugal mechanism to obtain better economy curves. This is shown in Fig. 3 where its rotation causes a sleeve II to slide in a bear- 'Ihe sleeve I I carries a rotating shaft tion to the speed of the engine. Governor weights I5, one of which is shown pivoted at I6, rotate clockwise at high speed compressing the spring 2 I1 and ultimately engaging with a stop 14 l0- cated in a rotating arm 15.

A cam face 2l on the weight I5 engages with the roller I8 mounted on the rotating element I9. A light spring 2li causes the roller I8 to be held in contact with the cam face 2 I. By this means, as the weight I5 rotates clockwise, the roller I8 is moved to the left the desired amount, thus compressing thespring 28 and sliding a shaft 23 to the left which engages with a number of barometric elements 23, which are located in a chamber 24 which is in communication through a pipe 25with the pressure on the engine side of a throttle 61 in an air entrance 19. The pressure in the chamber 24 is usually described as at manifold air pressure (see Fig. l). The reason for this is that a supercharger is generally used, in which case this connection 25 is on the engine side of the supercharger (not shown) which is usually located just before the inlet valve air entrance to the engine cylinder. To simplify the disclosure the supercharger is not shown. The barometric element 23 engages on the right with the sliding shaft 22 and on the left with a servomotor valve 216 which, in its turn, engages with a compression spring 34, which takes up the back lash between the valve 26 and the barometric element 23 and the sliding shaft 22. 'I'he governor characteristics are controlled by the spring I 1 slightly modified by the springs 20v and 34.

The movement to the left of the valve 26 causes a piston 21 to move to the right in the cylinder 28. Oil under pressure is admitted to the servomotor through the pipe 53 and when the valve 26 is moved to the left, as it is when there is a decrease of pressure in the chamber 24, oil flows down a passage 54 and pushes this piston 21 to the right. The oil at the right of the piston 21 then escapes through a passage 55 through the valve 26 to an o-il outlet 56.

A rod 51 is pivoted to the guide 58 which is connected to a piston rod 59 mounted on the piston 21. The rod 51 is connected to a link 58 mounted on a bracket 52 (Fig. 2). The link 58 is formed in the shape of a crank and is connected to a link 50 (Fig. 2). The link 60 is connected to the throttle arm 6I (Fig. 1) through a pin 62 on the end of which is a ball'63. The ball 63 slides in a slot in the element 54. 'Ihis element 54 is connected to the rod 41 which is pivotally mounted on the control lever 36. lA lever 65 is mounted on a pivot 6E, which pivot is mount` ed on this main speed control lever 35. This lever carries a link 48 which slides inside the element 64. Arounded end 68 of the link 48 en- The order to free the device from the servo-v motor and prevent interference with the above mentioned manual means for closing the throttle, a by-pass valve 29 is provided which gives a free opening 35 between the passages 54 and 55 when this Valve is rotated anti-clockwise about 45 (Fig. 3) In the position shown, which is the operative position, a small opening 3| causes the device to function as described above, but permits a circulation of a small quantity of oil at all times in addition to that which leaks around the piston 2l. A by-passpassage 32 connects the passage 54 with the valve 29 and a by-pass 35i connects the passage 55u/'ith the valve 29.

A rod 46 is pivotally connected tothe lever 65 at the point which is normally located opposite a pivot 6i on which the lever 36 ismounted and rotated (Fig. l). Hence, rotation of the lever 36 does'notnormally move the link d6. The link travels with the link 4l' and at a slightly faster rate than vthe link d'7, and hence slightly faster thanthe element 64. The link 6 is connected with the lever 62 to the valve 29. Hence, whenever the 'roller 38 rides on the surface 42 and Yis depressed, the valve 29 rotates anti-clockwise and the servomotorZE, 21, 59, 56, 51 is rendered inoperative. -At the same time the rounded end 68 engages with the ball 63 and the throttle 6l is thus closed manually.

In order to permit this servomotor to be rendered inoperative at any time and not merely whenthe lever 36 is rotated anti-clockwise into the position for minimum speed, a handle 35 on the throttle lever 35 is made so that it can be depressed and'when itis depressed, it'slides inside a cylinder l2 integral with-the lever 36, compressing a spring 13 and carrying with it the rod 43 and the roller 38. In order that the handle 35 can rotate without rotating the rod d3, a ball joint isprovided-on the end of the rod d3. In order-vthat-the handle 35 can be locked in the depressedV position, a pin 59] is provided in the `handle and an L-shaped slot 5i in the cylinder 12 is also provided. Hence, when the handle S5 isldepressed compressing the spring 73, the pin 5D is lowered to the level of the horizontalleg of the L-shapedslot 5|.y The handle 35 is then rotated anti-clockwise 'looking` down and the pin 5! iscarried over to the rightinside the L-shaped slot 5I. The roller 38 is thus locked in the lower position and the valve 29 is thus moved to permit Fig. 5 shows the relation between the revolutions per minute and the manifold air pressure measured in inches of mercury. As the revoluktionsper minute increase, the permissible manifold pressure increases. Hence,any increase in speed calls for an increase inmanifold pressure. V-The curve to the left shows the relation be- 4- tween the revolutions per minute of the engine and manifold air pressure for bestv economy, that is, the relation whichY exists when cruising lean and running the Vengine slower and opening the throttle wider than with the normal curve. When the cam I6 is rotated anti-clockwise, the manifold pressure follows the curve of better economy. The curve to the right shows the nor-v mal -curve with the cam liin the position as shown in the drawings, The slowe-ran engine runs at any given power, the less fuel it consumes as a rule.

Theadjustable stop it, Fig. 3, which is mounted on the rod varm 15 limits the maximum response toA speed of the 1centrifugal weightV lever l5, soas to limit the maximum boost pressure.

Otherwise, during a. dive an excessivey boost pressure would be possible. Points E and F (Fig. 5) represent the maximum boost pressures controlled by the adjustable stop 11i and the movable cam i6. The point 1E corresponds to nraximiim boost pressure with a normal Ycurve with the cam l@ in positionshown and the point F to the maximum 'boost pressure with the maximum economy curve with camV l@ rotated counterclockwise.

The inclined Vsurface 41 (Fig. 1') may be mounted on a slidable element 84 held on the quadrant se'by studs es and ae. The holes in the quadsides of the piston 2l'. comes inoperative during theidling position and Y rant 3Q may be slotted so that the exact location of the inclined surface il maybe adjusted.

Operation `When the speed'control lever" 36 is moved counterclockwise, the roller 38 rotates'on thefsuriace 46 down the inclined Ysurface flandalong the surface 132. When the throttle lever'361is moved in 'the anti-clockwise direction (Fig. -51), that is to say, in the idling position, .the `rod f4!! moves to the right and engages with Vthe v.ball end63 and closes the throttle lever'i, causing the throttle 6l to close. v'In OtherWordS, the 4control ceases to'be auto-matic. The `-end oi ith'e rod '48 is provided vwith the element 6% which is rounded to permit freedom of Vmoti-on in the "hollow element 64. When the control-lever Slis'in its low speed position, the end V68y kengages with the ball`63 which, in its turn, engageswith'the sliding element 69 and compresses the spring lil. The throttle llever '6I isfthus moved anti-clockwise and the throttle 61 is closed manually.

As the lever is rotated counter-clockwiseby the depression of the rod 43, it carries over to ie left the link 4`6which causes the lever 582 to rotate anti-clockwise and thus moves withitthe valve 29 inthe anti-clockwise direction, vwhich as described above,places the passage y303 (Fig. 3) in a positionto allow free communication on both The servomotor thus'behence no unusual eiiort is required'to close the throttle v'ito theidling position.

Let us assume thatthe engine isrun'ning Vat 1500 revolutions per minute 'and manifold air pressure corresponding tothe point A on the'normal curve oiFig. 5. vLet vus assume further that the throttle 67 is to Vbe openedgThisfis accomplished as follows: g y

The speed control lever 36 is. moved in the clockwise direction. The link'g 'acts'on the pro'- j peller pitch gear 'Tl-8u, Immediately the'rev'olutions per minute would increaseandthemanifold air pressure would fall to the point B, because the element 69 `wouldnot immediately engage' the ball'63. The lowered manifold air pressure is due to the increased air iiow at a given throttle and the fall in pressure causes the element 23 to expand. As a result, the valve 26 is moved to the left, thereby admitting oil pressure from the line 53 to the passage '54. The piston 21 then moves to the right carrying with it the rod 57. rThe rod il@ moves to the left carrying With it the pin 53 which moves the throttle lever 6| clockwise, opening the throttle 61 and raising the manifold air pressure in 30 and hence in pipe and in the chamber 2li, to the point C, which would also be located on the normal curve. Meanwhile, the governor il maintains the speed of the propeller constant at the speed determined by the position of the lever 30.

If this point C is not on the desired normal curve, it is corrected by changing the contour of the cam surface 2i. When the cam l0 is moved to the left counter-clockwise and the sleeve il moves to the left at any given speed, the capsule 23 is translated to the left, carrying With it the valve 2S, compressing the spring 34. Oil pressure then ilows down the pipe 53, passage 54, the piston 21 moves to the right, the link 60 moves to the left carrying With it the ball 53. The throttle 51 is then moved towards the wide open throttle position, but the link 49 is not moved and therefore, the revolutions per minute of the engine remain stationary and therefore, the point C moves up to point D. The point D is vertically above the point C because the speed is constant and the distance C-D corresponds to the distance between the tvvo curves, the better economy curve and the normal curve. The capsule responds to changing pressures virtually on a straight line; hence the cam l0 need be calibrated for only tvvo positions.

The probable relationship is that point A corresponds to 23" mercury at 1500 R. P. M.; point B corresponds to 22" mercury at 1700 R. P. M.; point C corresponds to 26 mercury at 1700 R. P. M.; point D corresponds to 29" mercury at 1700 R. P. M.; point E corresponds to 40" mercury at 2350 R. P. M.; and point F corresponds to 45 mercury at 2350 R. P. M.

What I claim is:

1. In combination With an internal combustion engine having an air entrance and a throttle valve therein adapted to control the air oW to the air inlet of the engine, a variable pitch propeller driven by said engine and an engine-driven, variable speed centrifugal governor for controlling the engine speed by varying the pitch of said of the engine by varying the pitch of the propeller, a throttle lever, an automatic controlling device therefor comprising a second engine-driven centrifugal governor, a barometric device operatively connected to said second centrifugal governor and slidably mounted so that it is moved bodily thereby, a variable pressure chamber enclosing said barometric device and connected to the air inlet so as to be maintained at the pressure of the air entering the engine, a source of iiuid under pressure, a servomotor valve operatively connected to the barometric device and to the second governor so constructed and arranged that it controls the now of said fluid under pressure, a servomotor operatively associated with said servomotor valveand adapted to be operated by said fluid under pressure and by said servomotor valve, a link connection from said servomotor to said throttle lever adapted to move the throttle so as to maintain the pressure in the air entrance to the engine at the pressure required to move the servomotor valve into its neutral position.

2. A device as set forth in claim 1 in which there is a casing supporting said automatic mechanism and in which second centrifugal governor is slidably mounted with respect to said casing, means for sliding the second centrifugal governor, the pressure responsive device and the servomotor valve laterally so as to vary the pressure automatically maintained in the air entrance to the engine with each speed of the engine.

3. A device as set forth in claim 1 in which there are additional valve means so located that when open it renders the servomotor inoperative, manually controlled mechanism for said valve mounted on said manually operated control device and so constructed and arranged as to be operated at vany position of said control device, a yieldable link connecting the throttle with the manually operated device and adapted to manually control the throttle lever when said servomotor is inoperative,

4. A device as set forth in claim 1 in which there are additional valve means so located that when open it renders the servomotor inoperative, a link connected to said valve and to said manually operated control device, a second link also connected to said manually operated device and so constructed and arranged as to push the throttle lever into the closed position when the manually operated control device is set in the position of minimum speed of the engine so that the throttle may be easily closed Whenever the automatic throttle control device is disconnected.

CARL F. SCHORN. 

